The present invention relates generally to the field of fluid transfer, and more specifically to submersible and surface pump apparatus and methods of making and using same.
Electrical submersible pumps (ESPs) are used for artificial lifting of fluid from a well or reservoir. An ESP typically comprises: (1) an electrical submersible motor—which is the driver—each motor may be up to about 30 feet in length, with multiple sections of motors available based on the power requirement; (2) a seal section (sometimes referred to in the art as a protector)—which functions to equalize the pressure between the inside of the system and the outside of the system and also acts as a reservoir for compensating the internal oil expansion from the motor; and (3) a submersible pump—the driven portion—having one or more pump stages inside a housing. One pump may be 24 feet or more in length, and multiple identical pump stages may be installed based on the pressure that has to be developed. The order in which the sections are typically installed in the well is motor, seal section and pump, but alternative arrangements may be used. Each pump stage is capable of producing certain pressure (head) which is cumulative—for example, if a stage can produce 20 feet of head, 100 stages will produce 100×20=2000 feet of head.
In a variety of applications, it is advantageous to utilize a surface pump, such as a horizontal pumping system (“HPS”), which generally includes a driver, which may be a motor, turbine, diesel or non-diesel internal combustion engine, generator, and the like, in some cases combined with a protector, seal chamber, and the like, and a pump mounted on a horizontal skid. For example, an HPS may be used in applications such as water floods, liquid propane injection, water supply, booster service, salt water disposal and crude oil transfer.
Whether used in surface applications or downhole, each pump stage has definite performance characteristics limited by and/or based on the slope of head versus flow rate curve, amount of head (lift) produced, efficiency, brake horsepower, and down thrust. For gas handling in downhole applications, a taper pump unit approach has been used. A taper pump unit consists of two or more pump housings, each pump housing having different pump stages in it. Taper pumps can not overcome the limitations of a single pump stage.
From the above it is evident that there is a need in the art for improvement in surface pumps and downhole pumps, such as electrical submersible pumps.